A method for the estimation of normative bone surface area to aid in objective CT-based fracture severity assessment

The reliable assessment of fracture severity plays a critical part in treatment, providing essential information to guide clinical decision-making. However, current classification schemes such as the AO/OTA are constrained by limitations intrinsic to subjective categorical systems. A recently developed objective CT-based assessment methodology quantifies fracture severity by calculating the mechanical energy expended during bony fragmentation. Specifically, fracture energy is determined by comparing the bone free surface area in the fractured limb to that in the intact contralateral limb. Unfortunately, the contralateral limb is not routinely scanned in the course of fracture assessment. Consequently, fracture energy can not be obtained, since there is no datum against which to compare the fractured limb. To facilitate the application of this novel technique to large multi-center and retrospective studies where the intact contralateral CT scan is unavailable, this study aimed to establish a normative, anthropometrically scaled intact bone model to be used as a substitute datum. A mathematical model that estimated free bone surface area along the intact contralateral limb was regressed from a study group of 22 tibial plafond fracture patients. The regressed tibia model provided suitably accurate estimates of the directly measured intact surfaces areas (average error of 15%). The differences between regressed and actual bone surface areas did not ultimately affect the stratification of fracture severity, as fracture energy measures using the regressed model maintained a 0.90 concordance with the original analysis. The results from this study suggest that normative bone surface area can be incorporated into the novel CT-based objective fracture severity assessment technique.